ISO 9815:2010

Road vehicles — Passenger-car and trailer combinations — Lateral stability test

ISO 9815:2010 specifies a lateral stability test for passenger-car and trailer combinations. It is applicable to passenger cars in accordance with ISO 3833, and also to light trucks, and their trailer combinations. The lateral stability test determines the damping characteristic of the yaw oscillation of such towing-vehicle–trailer combinations excited by a defined steering impulse. The combination is initially driven in a steady-state, straight-ahead driving condition. Oscillation of the vehicle is then initiated by the application of a single impulse of steering, followed by a period in which steering is held fixed and the oscillation of the combination is allowed to damp out. Testing is conducted at several constant speeds. Where non-periodic instability is of interest, a steady-state circular test is specified.

Véhicules routiers — Ensembles voiture particulière et remorque — Essai de stabilité latérale

General Information

• Status: Published
• Publication Date: 29-Apr-2010
• ICS: 43.100 - Passenger cars. Caravans and light trailers
• Technical Committee: ISO/TC 22/SC 33 - Vehicle dynamics and chassis components
• Drafting Committee: ISO/TC 22/SC 33/WG 2 - Vehicle dynamics of passenger cars
• Current Stage: 9092 - International Standard to be revised
• Completion Date: 21-Jun-2021

Relations

• Revises: ISO 9815:2003 - Road vehicles — Passenger-car and trailer combinations — Lateral stability test
• Effective Date: 11-Apr-2009

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 9815
Third edition
2010-05-01

Road vehicles — Passenger-car and
trailer combinations — Lateral stability
test
Véhicules routiers — Ensembles voiture particulière et remorque —
Essai de stabilité latérale




Reference number
ISO 9815:2010(E)
©
ISO 2010

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ISO 9815:2010(E)
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ISO 9815:2010(E)
Contents Page
Foreword .iv
Introduction.v
1 Scope.1
2 Normative references.1
3 Terms, definitions and symbols .1
4 Measurement variables.2
5 General conditions .2
5.1 Compliance .2
5.2 Measuring equipment .2
5.3 Test track.3
5.4 Wind velocity .3
5.5 Loading conditions .3
6 Test method .5
6.1 General .5
6.2 Test runs.5
7 Data analysis.7
7.1 General .7
7.2 Individual test runs.8
7.3 Zero-damping speed .10
7.4 Reference-damping speed.10
7.5 Reference-speed damping.11
8 Data presentation .11
8.1 General data.11
8.2 Test conditions .11
8.3 Results.11
Annex A (normative) Test report — General data (supplement to ISO 15037-1:2006, Annex A).12
Annex B (normative) Test results.15
Annex C (normative) Steady-state behaviour.16
Bibliography.17

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ISO 9815:2010(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 9815 was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 9, Vehicle
dynamics and road-holding ability.
This third edition cancels and replaces the second edition (ISO 9815:2003), which has been technically
revised.
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ISO 9815:2010(E)
Introduction
The main purpose of this International Standard is to provide repeatable and discriminatory test results.
The dynamic behaviour of a road vehicle is a very important aspect of active vehicle safety. Any given vehicle,
together with its driver and the prevailing environment, constitutes a closed-loop system that is unique. The
task of evaluating the dynamic behaviour is therefore very difficult since the significant interaction of these
driver-vehicle-environment elements are each complex in themselves. A complete and accurate description of
the behaviour of the road vehicle must necessarily involve information obtained from a number of different
tests.
Since this test method quantifies only one small part of the complete vehicle handling characteristics, the
results of these tests can only be considered significant for a correspondingly small part of the overall dynamic
behaviour.
Moreover, insufficient knowledge is available concerning the relationship between overall vehicle dynamic
properties and accident avoidance. A substantial amount of work is necessary to acquire sufficient and
reliable data on the correlation between accident avoidance and vehicle dynamic properties in general and the
results of these tests in particular. Consequently, any application of this test method for regulation purposes
requires proven correlation between test results and accident statistics.

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INTERNATIONAL STANDARD ISO 9815:2010(E)

Road vehicles — Passenger-car and trailer combinations —
Lateral stability test
1 Scope
This International Standard specifies a lateral stability test for passenger-car and trailer combinations. It is
applicable to passenger cars in accordance with ISO 3833, and also to light trucks, and their trailer
combinations.
The lateral stability test determines the damping characteristic of the yaw oscillation of such towing-vehicle–
trailer combinations excited by a defined steering impulse. The combination is initially driven in a steady-state,
straight-ahead driving condition. Oscillation of the vehicle is then initiated by the application of a single
impulse of steering, followed by a period in which steering is held fixed and the oscillation of the combination
is allowed to damp out. Testing is conducted at several constant speeds. Where non-periodic instability is of
interest, a steady-state circular test is specified.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 1176, Road vehicles — Masses — Vocabulary and codes
ISO 2416, Passenger cars — Mass distribution
ISO 3833, Road vehicles — Types — Terms and definitions
ISO 4138:2004, Passenger cars — Steady-state circular driving behaviour — Open-loop test methods
ISO 8855, Road vehicles — Vehicle dynamics and road-holding ability — Vocabulary
ISO 15037-1:2006, Road vehicles — Vehicle dynamics test methods — Part 1: General conditions for
passenger cars
3 Terms, definitions and symbols
For the purposes of this document, the terms, definitions and symbols given in ISO 3833, ISO 8855 and the
following apply.
3.1
yaw articulation angle
∆ψ
angle of the X axis relative to the X axis, i.e. angle between the X axes of each of the two units, with the
C T
polarity determined by the rotation of the towing vehicle relative to the trailer
NOTE The letters “C” and “T” are used as subscripts to distinguish between variables associated with the towing
vehicle (car or light truck) and the trailer, respectively. For example, the longitudinal axis of the intermediate axis system of
the towing vehicle is designated as X , and the lateral acceleration of the trailer is designated as a .
C YT
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ISO 9815:2010(E)
3.2
mean gradient (of the test track)
G
change in elevation of the track surface between two points along the path of the vehicle divided by the
horizontal distance between those points, where the two points are those that define, as closely as is
practicable, that segment of the track travelled by the test vehicle between the times t and t , respectively
2 ∆ψn
For t and t , see 6.2.2 and 7.2.3, respectively.
2 ∆ψn
NOTE This gradient is dimensionless and is positive for a test vehicle travelling uphill and negative for a test vehicle
travelling downhill.
4 Measurement variables
When performing this test procedure, the following shall be measured:
⎯ steering-wheel angle, δ ,
H
⎯ longitudinal velocity of the towing vehicle, v ,
X
⎯ lateral acceleration of the trailer, a ,
XT
⎯ yaw articulation angle between towing vehicle and trailer, ∆ψ.
The following should be measured:
dψ
C
⎯ yaw velocity of the towing vehicle, ;
dt
dψ
T
⎯ yaw velocity of the trailer, .
dt
NOTE These variables are not intended to comprise a complete list.
5 General conditions
5.1 Compliance
The general conditions of the test shall be in accordance with ISO 15037-1, with the additions and exceptions
given in this clause.
5.2 Measuring equipment
The measurement variables given in Clause 4 shall be monitored using appropriate transducers. The
requirements of ISO 15037-1 regarding measurement and recording equipment shall be applied to both
towing vehicle and trailer. Typical operating ranges and recommended maximum errors for variables not
considered by ISO 15037-1 are given in Table 1.
A steering-wheel stop or marking may be used. The use of a steering machine is optional.
Table 1 — Variables, operating ranges and recommended maximum errors —
Addendum to ISO 15037-1:2006, Table 1
Recommended maximum error
Variable Typical operating range
(of combined transducer/recorder system)
Articulation angle ± 20° ± 0,2°
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ISO 9815:2010(E)
5.3 Test track
In addition to the test track requirements of ISO 15037-1, the mean gradient of the test track along the path of
the vehicle, G , shall be within the range ± 0,01. G shall be recorded for each test run. See 6.2.1 and 7.2.1 for
related requirements. In addition, the test surface shall be maintained over a track with a minimum width of
8 m. An increased run-off area should be provided in addition to the specified test surface.
Inasmuch as yaw damping of articulated vehicles is known to be sensitive to the longitudinal slope of the test
track, the test should be conducted in both directions whenever G approaches the allowed maximum.
5.4 Wind velocity
Wind velocity shall be in accordance with ISO 15037-1 and, in addition, should not exceed 2,5 m/s.
5.5 Loading conditions
5.5.1 Towing vehicle
The total mass of the towing vehicle shall consist of the complete vehicle kerb mass (ISO 1176, code
ISO-M06) plus driver and instrumentation (combined mass should not exceed 150 kg). The location of the
instrumentation shall be such as to minimize its effect on the yaw moment of inertia of the towing vehicle.
The tests should be repeated at a maximum loading condition of the towing vehicle or at other loading
conditions of interest or all these. For the maximum loading condition, the total mass of a fully laden vehicle
shall consist of the complete vehicle kerb mass plus 68 kg for each seat in the passenger compartment, with
the static load at the coupling ball and the remaining maximum luggage mass equally distributed over the
luggage compartment in accordance with ISO 2416. Loading of the passenger compartment shall be such that
the actual wheel loads are equal to those obtained by loading each seat with 68 kg in accordance with
ISO 2416. The mass of instrumentation shall be included in the vehicle mass. Care shall be taken to ensure
that the moments of inertia are representative of the loading conditions of the vehicle in normal use.
The total mass of the fully laden towing vehicle, including the equivalent mass of the static load at the coupling
ball, shall not exceed the maximum design total mass (ISO 1176, code ISO-MO7), nor shall the front and rear
axle loads exceed their respective maximum design values with the load applied at the coupling ball. If a load-
distributing coupling is used, these axle loads should be assessed after engagement of the load-distributing
mechanisms (see 5.5.4), except where this is counter to the recommendations of the manufacturer of the
towing vehicle.
5.5.2 Trailer
The trailer shall be loaded to its maximum authorized total mass (ISO 1176, code ISO-M08) or until the
maximum design mass of vehicle combination (ISO 1176, code ISO-M18) is reached, whichever is the lesser
of the two masses. If the type of trailer allows various load distributions, the load shall be distributed in such a
way as to produce realistic and representative values of the yaw moment of inertia, centre-of-gravity height
and the static load at the coupling ball (see 5.5.3).
Optionally, tests may also be carried out with any other towed mass of interest.
The mass, centre-of-gravity position and yaw moment of inertia of the trailer as tested shall be measured and
noted in the general data (see Annex A). Alternatively, a description of the loading condition, adequate to
reproduce these properties with reasonable accuracy, shall be provided.
5.5.3 Static load on the coupling ball
Tests shall be carried out with the maximum permissible static load on the coupling ball as determined by the
maximum coupling load allowable for the towing vehicle, the trailer or the coupling itself, whichever is the
smallest. However, it is necessary to reduce further the static load on the coupling ball if it causes the load on
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ISO 9815:2010(E)
the rear axle of the towing vehicle to exceed the maximum design load as specified by the manufacturer of the
towing vehicle. Unless it is counter to the recommendations of that manufacturer, the rear-axle load is to be
assessed after the engagement of any load-distributing mechanism at the coupling.
The fraction of the weight of the trailer carried as static load on the hitch has an important influence on the
yaw damping of the vehicle combination. Typically, damping decreases as static load on the hitch decreases.
Therefore, tests should also be carried out with the minimum permissible static load at the coupling ball (see
[1])
ISO/TR 4114 .
5.5.4 Adjustment of load-distributing coupling mechanisms
When trailer mass is large, load-distributing couplings are often used to restore the pitch angle exhibited by
the towing vehicle prior to the application of a static load on the coupling. The addition of this moment
redistributes some of the coupling static load from the rear tyres to the front tyres of the towing vehicle and the
trailer tyres. This increases the articulation-angle damping but reduces the understeer of the towing vehicle
with lateral acceleration.
The load-distributing coupling often includes a mechanism for adding articulation-angle damping. The coupling
and auxiliary friction devices should be installed and adjusted according to the towing vehicle, trailer and
coupling manufacturers' recommendations.
In the absence of manufacturers' recommendations for the use of load-distributing coupling, the following
procedure should be followed. Prior to the attachment of the trailer, measure the vertical distance from points
on the vehicle body to the ground at the centre lines of the front and rear axles of the towing vehicle, with the
vehicle loaded as intended for testing. After attaching the trailer, adjust the coupling moment such that the
resulting overall changes in these two vertical distances are the same within 10 mm.
If recommendations for static loading conditions are not available for the load-distributing coupling, static load

can be based upon the recommendation of Reference [2], which is that coupling load should be 8,4 % of the
weight of the towing vehicle.
NOTE With multi-axle trailers, the force required to support the tongue may increase as the height of the tongue is
increased. As a result, proper set-up of the static load on the coupling ball and coupling moment can be an iterative
process.
The coupling moment should be recorded for the test configuration. For this, the front and rear axle loads of
the towing vehicle should be measured once without the trailer attached (to determine the weight of the towing
vehicle) and once with the trailer attached and the load-distributing coupling adjusted. The axle loads shall be
measured with the trailer and towing vehicle on a flat surface. If the contact patches of the towing-vehicle and
trailer tyres are not in the same plane, the coupling moment is altered.
The moment due to a load-distributing coupling, M , can be calculated as follows:
Yeq
M=+Fl()e+F (e)−mg(d+e)
YZeq wfC C C ZwrC C C C C
where
F is the sum of the loads on the front wheels of the towing vehicle with the trailer attached and load-

ZwfC
distributing coupling engaged;
F is the sum of the loads on the rear wheels of the towing vehicle with the trailer attached and load-

ZwrC
distributing coupling engaged;
g is the gravitational constant;
m is the mass of the towing vehicle;
C
l is the wheelbase of the towing vehicle;

C
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ISO 9815:2010(E)
d is the longitudinal distance between the centre of gravity of the towing vehicle and the centreline
C
of the rear axle of the towing vehicle;
e is the rear overhang, the longitudinal distance between the spindle axis of the rear axle and the
C
centre of the coupling ball.
6 Test method
6.1 General
Prior to testing, the vehicle shall be warmed up,
...